When you say that you have a multisite solution, I understand you have multiple sites defined in the Sitecore <sites>
section like this:
<site
name="xyz"
hostName="xyz.com"
rootPath="/sitecore/content/site-a"
startItem="/home"
/>
<site
name="abc"
hostName="abc.com"
rootPath="/sitecore/content/site-b"
startItem="/home"
/>
You can add any custom properties to every site definition like:
<site
name="xyz"
hostName="xyz.com"
rootPath="/sitecore/content/site-a"
startItem="/home"
myCustomValue="custom value XYZ"
/>
<site
name="abc"
hostName="abc.com"
rootPath="/sitecore/content/site-b"
startItem="/home"
myCustomValue="custom value ABC"
/>
And then read it in the code
var value = Context.Site.Properties["myCustomValue"];